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Function 30h            Get Version Number

    Returns the DOS version number.

        Entry   AH = 30h
                (DOS 5.0+: AL = 0   Return BH = OEM number
                           AL = 1   Return BH = version flag)

        Return  AL    = Major version number
                AH    = Minor version number
                BL:CX = 24-bit user serial number
                        (zero if unused)
                BH    = OEM number
                        or
                        Version flag (DOS 5.0+):
                        bit 3 = 0: DOS runs in RAM
                        bit 3 = 1: DOS runs in ROM
                        other bits reserved (0)

    ------------------------------------------------------------------

    Used under DOS 3.30, this call would return AL = 03h and AH = 1Eh
    (30 decimal).


    Notes
    The version returned under DOS 4.0x may be modified by entries in
    the special program list.

    The version returned under DOS 5+ may be modified by SETVER; this
    version number can differ from the version number returned by
    function 3306h.

    The OS/2 v1.x Compatibility Box returns major version 0Ah (10).
    The OS/2 v2.x Compatibility Box returns major version 14h (20).
    The Windows/NT DOS box returns version 5.00, subject to SETVER.